So, is all light created equal? Recently, a fluorescent light manufacturer, eager to convince classroom gardeners of the value of their special Instant Sun fluorescent lights, sent tubes to classrooms willing to design and conduct experiments to compare their full-spectrum tubes with any other fluorescents.
We were somewhat curious about the light tubes themselves, but we were most interested in hearing about the issues, challenges, and learning that arose for students doing "consumer product testing" and for teachers facilitating that student inquiry. Reports continue to come in with widely varied conclusions about the lights. Read on for teachers' descriptions of how these young inquirers grappled with the scientific process.
Laying the Groundwork
Participating classrooms used a range of plants in their light experiments -- radishes, peas, lettuce, marigolds, geraniums, grass, cactus, to name a few -- raising some from seed and starting others from cuttings. Some grew experimental plants on one tier of a GrowLab and control plants on another tier. Other classrooms grew both on one level, devising ways to block the lights from interfering with one another.
"My inner-city fourth through eighth graders are quite skeptical of advertising claims," reports Chicago, IL, teacher Paul Scott, "and didn't believe that the Instant Sun bulbs would prove to be better than our regular GrowLab fluorescents." Paul adds that he didn't reveal which set of bulbs was which, so students would have a fair shot at comparing the two treatments.
Other teachers reported a similar problem with "bias," but with a very different slant. "It was hard not to get kids to take sides," reports Saginaw, MI, fourth-grade teacher George Thompson. "Because the brochure reported that the lights approximated sunlight, and students had already observed how plants seemed to thrive in real sunlight, they were sure the special lights would perform better."
Some of the enlightening investigations were set up as full-class experiments, others conducted by small groups or individuals, and some carried out by collaborations of multiple classes.
Teachers report a variety of thoughtful student questions and discussions on such topics as defining "good plant growth," what to observe, how to measure, and how to represent data. "We had several classes working together on the investigation," says Paul Scott. "When the data was first posted, some students noticed that there was no uniformity in the way people were taking measurements, and realized that we needed to establish a standard." His students agreed that the tallest marigold branch should be straightened and that measurement taken for the record. Another class reports being challenged to accurately measure irregular geranium stems, finally choosing lengths of string to do so.
Several teachers reported that students' preconceptions colored their objectivity during the investigation. "When the lights didn't perform as my sixth graders had predicted," reports Douglas, MA, teacher Sheryl Casey, they complained, "It's not working!" Sheryl seized the opportunity to ask kids to explain themselves and to facilitate a discussion about scientific objectivity.
The question of what consitutes best growth or healthy plants emerged in many of the classroom investigations. For instance, one classroom of Arizona students believed that the total weight of lettuce produced would be the most valuable measure of light success, while another classroom decided that taste was most important. And while most classes measured plant heights, a number of teachers reported students' challenging this by raising the question "Is taller really better?" "Students began to notice that plants under the full-spectrum tubes, while not actually taller, seemed prettier and healthier, reports Painted Post, NY, teacher Janice Glover. "This prompted a discussion of what they meant by that. On closer observation, students observed that the healthier-looking plants actually had more rich blue-green and fewer yellowing leaves."
George Thompson's students had previously raised healthy tomato plants, and used that experience to brainstorm a list of attributes they considered indicators of healthy plants. In addition to measuring height, stem thickness, and number of leaves, they created a scale to rank leaf color from darkest to lightest green.
Perhaps because students took seriously their challenge to do real-life research, or maybe because they're just good inquirers, it seems that we had a lot of vigilant scientists concerned about keeping their tests "fair." Watering was a topic that prompted debate and different tactics. In some classrooms students painstakingly watered each pot with the same amount of water every time, while others pondered whether this was the "fairest" treatment. Several classrooms finally decided that each plant had individual needs based on its growth rate, weekly location (due to rotations in the GrowLab), and so on. They decided that the most equitable system would be to water plants individually as needed, by feeling the soil for moisture.
While most participants agreed that plants should receive equal amounts of light, there were also different approaches to controlling this variable. Some students decided to measure the distance to the lights from the bottom of the containers, while others decided that they'd have to raise pots individually as some plants grew taller, so that the tops of all plants remained equidistant from the lights.
"As the investigation progressed, I was amazed at the degree to which my fourth graders critiqued their own scientific setup, notes George Thompson. "Perhaps because it was a real-life problem that we were testing for an actual company, students were especially concerned about the accuracy and integrity of their experiment." He reports that because there was little difference between the experimental and control plants, students searched extra-hard for flaws in their setup. "They began to notice, for instance, that the containers had different numbers of drainage holes, or that light from windowsills might be 'contaminating' the experiment."
Untangling Results and Making Connections
Did the Instant Sun tubes actually produce better, healthier, taller, or more desirable plants? Well, that depends who you talk to. We heard a range of conclusions, from "they didn't make a lick of difference" to "we've never grown such lush and healthy plants." Some classes found that the "control" plants prevailed, while others reported that, although the Instant Sun tubes produced somewhat stockier, healthier-looking plants, they weren't convinced of their value. "Although my students found that the experimental plants were slightly taller and had thicker stems, when we factored in the significantly higher price of the experimental lights, students unanimously agreed that they didn't seem worth the extra expense."
"My students realized that there were other things that affected plant quality or desirability -- even beyond the factors we had been carefully recording," reports Allendale, NJ, teacher Barbara McGuirk. Seeking some data on less "measurable" qualities, students decided to survey other school members to determine which plants people subjectively preferred. They invited students and faculty to vote for the plant they preferred from each pair of matched experimental and control plants. "We discovered that people chose the experimental and control plants nearly equally," she adds. "The kids discovered that, rather than height or leaf number, the participants seemed to prefer plants that had flowers on them."
"Our marigolds and zinnias growing under Instant Sun tubes were taller and bloomed earlier than the others," reports Paul Scott. This sparked a discussion of whether blooming faster was actually a positive outcome. Students agreed that it would be a positive outcome if, for instance, you're a grower wanting to make money selling blooming plants. "Students realized that in other cases, delayed, but longer, blooming might be preferable," he adds.
Several teachers reported helping students understand that they could only make valid conclusions based on the particular plants and conditions used. "When students realized we couldn't necessarily generalize to other types of plants or conditions, it prompted them to discuss other plants, lighting conditions, and variables they might change if they were to do it again," one participant reported.
If not the definitive answer to the question, Which are the "best" lights?, what did students gain from this experience? In addition to an increased focus on keeping tests "fair" and objective, many teachers report their students developed greater comfort with the ambiguity and complexity of the scientific process, and with the notion that there is not always one right, easy-to-find answer. "I found this type of real-life challenge to be very involving for the students," says Paul Scott. "By hearing their discussions and struggles in setting up fair tests and trying to make sense of data, I learned more about what I should focus on to support their understanding of the scientific process."
We believe that projects like these can encourage students to have a healthy skepticism, questioning what they read and hear, and to develop confidence in their investigative skills. We will continue to suggest relevant challenges, encourage your participation, and look forward to hearing about your students' experiences as inquirers.